Botrylloides is a genus of ascidian tunicates in the family Styelidae. Like Botryllus, Botrylloides are flat sheets of organisms which can be found covering ropes, boat hulls, horseshoe crabs, seaweeds, and any still or slow-moving object in saltwater. Also both are considered to be invasive Ascidians, found in many ports around the world. Invasive tunicates such as these, Didemnum sp., and Styela clava are a problem for shellfish and other marine life populations, and cause fouling of boats and piers. Species within the genus Botrylloides include: